iCloud storage full due to Docs and Data. However, no Docs visible in iCloud Drive on devices.

Dear Community,

I receive the message that my iCloud storage of 50GB is full. Most of the data (over 30GB) is shown in Settings as data from Docs.

However, neither on icloud.com nor on my devices syncing with iCloud, I can see that much doc data in the iCloud drive app...

So where does it come from? And how do I get rid of it?

Thanks in advance!